Evolution Exam 3 Review Questions 1 Concerted evolution is a process that may explain the observation that paralogous genes within one species are more closely related to each other than members of the same gene family in another species a Paralogous separated by a gene duplication event if a gene in an organism is duplicated to occupy 2 different positions in the same genome then the 2 copies are paralogous 2 Gene families originate through concerted evolution An example of a gene family is that of the globin genes 3 Evidence that nucleotide sequence variation within the antigen recognition site of the human MHC gene is driven by natural selection is that a The replacement rates exceed synonymous rates at the antigen recognition site b Extraordinary levels of polymorphism high levels of diversity Substitution rate is much higher than you would expect from a neutral gene o Recognition sites recognize pathogens therefore faster substitution rates Synonymous rates give calibration o Slower purifying selection weeding out deleterious o Faster increases selection 4 Trivers principle measures the energetic cost of the parental expenditure that benefits one offspring at a cost to parents ability to invest in other components of fitness a Ex sperm cheap ova not cheap b Energetic cost the higher of the two is the limiting resource Batemans principle Theory that females almost always invest more energy in producing offspring than males and are therefore the limiting resource over which sex will compete whichever gender has the steeper relationship between reproductive success and mating success will have stronger selection 5 Factors that drive female choice a Appearance b Displays are indicators of genetic quality c Acquisition of resources d Preexisting sensory biases For males o If males were extremely discriminating I would assume they were the limiting resource and therefore the female would not be discriminating 6 Paralogous 2 genes that are duplicated and then diverge in sequence a Ex Alpha and Beta globin clusters in humans Orthologous homologs found in different species 7 Evidence for tectonic movement a Patterns of age of material on ocean floor b Patterns of magnetic field orientation near ocean ridges c Orientation and position of the magnetic poles in rocks of different ages d Basement geology of continental edges 8 The Pleistocene Ice Age was driven by humans The most persuasive line of evidence for this is that it was driven by human hunting because extinction was selective on mass Evidence is consistent with the fact that Neanderthals Homo Sapiens DID cause this extinction to a significant extent 9 Adaptive evolution may take different paths to the same end because there are different a Very selective we ate the big ones ecological physical and chemical challenges a Character evolution is NOT predictable 10 Irreducible Complexity a A single system composed of several well matched interacting parts that contribute to the basic function wherein the removal of any one part effectively causes the system to ceases functioning i Ex Krebs cycle 11 Fitness of a pathogen R B S D y B transmission rate S of susceptible hosts D death rate of successive individual Y rate at which infected individual recover and become immune R of new cases produced by one infected host in a population o Selection works to make R as large as possible Trading off B and D o Treatments Vaccinations decrease S below a threshold value Wash hands reduce B 12 Won t need to know double first cousins on test a First cousins r 1 8 i Two paths connect them one through the grandmother and one through the grandfather ii r n n of arrows 13 Kin Selection investments contribute to the fitness of relatives Evidence of Kin Selection in nature Ex Lions live in prides where the females are usually full sisters and they invest in their sisters offspring Individual selection benefits of aggregation with little cost easily explains loose or transient associations Ex group migrations reduced risk of predation with little cost of being in a group Group selection investments contribute to unrelated individuals with a net benefit to the actor because of net benefit derived from living in a group You receive the benefit because of action of the group Ex Collaboration of humans 14 Codon bias is highly nonrandom and occurs in the direct selection of synonymous mutations Codon bias suggests that some synonymous mutations are not selectively neutral a It is strongest in highly expressed genes Natural selection for translational efficiency 15 Hamiltons rule for inclusive fitness a The fitness benefit of altruism relative to its cost must exceed the reciprocal of the relatedness between actors b c 1 r 16 Multigene families a Gene clusters tandemly repeated genes located in one place or as groups of tandem repeats scattered around the genome i Ex histone gene clusters 17 18 Quantitative characters do not evolve in regular fashion a Periods of rapid change that punctuate relatively no change b Most change occurs early in a lineages history i Bottom heavy rapid early change ii Change per generation slower heterozygote rate of change long periods of stasis with short periods of rapid change 19 Neutral alleles pseudogenes are constant on per generation time a Absolute time Not neutral alleles under selection 20 There is evidence that adaptive evolution has occurred in homo sapiens after the first fossil record time a Homo sapiens co occurred with other members of the genus about 3 4 at same i Indigenous Africans have the deepest branch from rest of the world Can trace lactase persistence allele to 3 instances in evolution o This is the best evidence that physical evolution has continued 21 Virulence through a vector is higher than in a pathogen that is directly transmitted 22 Darwinian medicine is the application of modern evolutionary theory to understanding health and disease a Key assumptions i Phenotypes are products of gene environment interaction ii Humans have not stopped evolving Deals with the notion why humans are now prone to obesity because back then we would hunt our food and eat for a couple days and then have to go a long time before eating again Our bodies evolved from a different time in different conditions 23 Pseudogene non functional version of a particular gene found in spatial proximity on the chromosome to the functional version of a gene a Evidence these were once active genes i Sequences correspond tightly ii